Waterproof leather board and process of preparing the same.



' UNITED STATES PATENT OFFICE.

EDGAR S. IBU'FPUM, DE NEWTON, AND WILLIAM W. CARTER, OF NEBDHAM,MASSACHU SETTS, ASSIGN'ORS' TO THE NEWTON COMPANY, OF NEWTON,-MASSACHUSETTS, A

CORPORATION OF MAINE.

WATERPROOF LEATHER BOARD AND PROCESS OF PREPARING THE SAME.

1% Drawing.

Specification of Letters Patent. Application filed January 29, 1909.Serial No. 474,966.

Patented July 26, 1910.

To all whom it may concern:

Be it known that we, EDGAR S. BUFFUM,

residing at Newton, in the county of Mid-' dlesex and State ofM'Sssachusetts, and WIL- LIAM W. CARTER, residing at Needham, in thecounty of Norfolk and State of Massachusetts, both citizens of theUnited States,

have invented certain new and useful Improvements in Waterproof LeatherBoard and Processes of Preparing the Same, of which the following is aspecification.

/ f This invention relates to the waterproofof leather fibers only, orwhether it is made up in part from such fibers and in part from fibersof other material suitablefor the pun.

pose; I I

it has long been desired to produce an edective and homogeneouslywaterproof leatherboard, but sofar as we are aware no one has eversucceeded in accomplishing this result prior to our present invention,and we believe that those ,Who have dealt with this iroblem have failedto recognize the wide distinction between leather fibers, on the onehand, and Vegetable fibers such as form the basis of ordinary paperyonthe other hand. The leather is oi animal origin and nitrogemodified bythe tanning process,-which has entirely changed the normal relations ofthe animal fiber substance to water, the fibers having lost theircolloidal character and dil with it their power of becoming greatlydistended by absorption of water whether pure water or water containingother substances in solution.

We have discoveredthat a thoroughl andhomogeneously waterproofed'leather oard results from our process, which consists essentially insubjecting the pulp fibers to an alkaline treatment and thenprecipitating upon and throughout the fibers suitable waterproofingagents in an amount sufiicient to produce an actual permanentwaterproofing: of the final product when finishedi- We be lieve that theresult of'the jalkalin'e treatment is greatly'to increase thereceptivity of the leather fibers to the waterproofing agents, and thisis-probabl'y due to the effect I of the alkaline treatment in'restoringto a substantial extent the. ori inal colloidal character of the leatherber substance treated, whereby the action of the waterproofing a ents isrendered vastly more effective. T e alkali used in our process also hasthe important function of neutralizing and converting into soluble saltsthe acids, '21. e., the tannic acid, chromic acid or their equivalents,Which were employed in sheeting the transformation of the raw-hide intoleather, thereby preventing the remature precipitation of the waterproong com-- pounds Within the pulp mixture, as well as removing the acidsfrom the leather fibers and leaving them receptive to the water--proofing treatment as already indicated.

It is an important feature of our process that the treatment is appliedto the disintegrated fibers of the pulp materials employed and may becarried'on'in the beater, thereby securing. a very thoroughincorporation: of "the various chemicals employed with the fibers of thepulp. We will now describe the processin iwhat we have found to be ahighly satisfactory and eificient form, but it will be understood, ashereinafter explained, that instead or using insoluble compounds of thefatt acids as the waterproofing agent other well :sizing agents may beemployed for the purpose, neous in character, and has been profoundlyown The process is carried on in a heater or ihollander, in which thepulp mixture is ground in the usual manner until it attains the desireddegree of: fineness. ;ture is then added an alkaline substance ;such ascaustic soda or potash, ammonia, llime, sodium carbonate, gate, borax orthelike alkaline treatment is that the various acids;

To this mixotassium carbonne result of this and weak acid com ound'scontained in the mixture, and particularly the tannic' or chromeaclds'contained in or derived-fromthe leather, combine'with thealkalineneuatralizingagent employed and thereafter exist in the mixtureas solublesalts of the alkali used.- With the mixture produced asjustidescribedthe're is mixed it solution of 'jsoap; in which term weinclude "any com- ,pound Whichis soluble in water orwin the pulpmixture-and is formed by thechemical? .mix a soluble sulfi union of analkali (sodium, potassium or ammonium) with one or more of the fattyacids, 2'. e., the acids of the fats, oils and resins. The mixture thusproduced is operated upon in the beater long enough to secure an equaldistribution of the soap upon the fibers of the pulp, about an hourbeing usually required for this purpose, and

there is then added thereto a precipitant which will react with the soapand form by the union of the fatty acids with the base of theprecipitant a compound which is insoluble in water or in the liquidportion of the pulp mixture. Among the precipitants which may be usedare alum, aluminum sulphate, and copperas, any of which compounds willre-act with the soap as above set forth and deposit an insolubleprecipitate upon the fibers of the pulp. The pulp mixture is thenoperated upon in the beater for another interval, usually about an hour,and is thereafter treated in the usual manner to produce the desiredsheet or other article by the employment of machines such as arecommonly used for this purpose.

In practice, the choice of the precipitant will vary according to thedesired color of the final product. For example, if a black leatherboardis desired, we use copperas for the preeipitanhin which case, if theleather in the pulp was bark-tanned, the soluble salts resulting fromthe alkaline treatment above referred to will re-act with the iron ofthe copperas to form a black coloring compound. If the leather waschrometanned and a black roduct is desired we with thepulp and thenemploy copperas' as a precipitant, with the same result. In this casethe soluble sulfid can bemixed with the soap and introduced therewithinto the pulp mixture. If the precipitant employed is alum, aluminumsulfate or calcium chlorid the resultin product will have, a natural orreddish co or. 1

The proportion of neutralizing agent employed must be governed largelyby the acidity ofthe pulp, and ordinarily'we employ soda ash for theneutralizing agent. According to our experience from 2 to 5 lbs. of drysoda ash for each hundred pounds of dry leather scrap or fiber willusually suflice for this purpose. The quantity of solid soap ordinarilyrequired is about 10% by weight of the leather scrap or fiber, and thequantit of precipitant used should be such as-wil r -act completelywiththe soap 60 or waterproofing compound and with that portion of the saltsformed by the union of the neutralizing a ent with-the acids derived-from the pp which can be recipitate'd by the precipltating agent; ehave found that ordinarily about one half of the last mentioned saltscan be precipitated, and

corresponding to the percentages of soda ash and waterproofing compoundabove given, the quantity of precipitant required will ordinarily befrom 8 to 13% by weight of the leather scrap, if copperas is theprecipitant employed, or from 6 to 10% by weight 'of the leather scrapif aluminum sulfate is the precipitant employed. It will be understoodthat the exact quantities and proportions of the neutralizing alkali,the soap and the precipitant will vary in different cases, and may bedetermined by chemical analysis of the pulp mixture.

The alkali necessary to effect the neutralization of the pulp mixturemay be mixed with the soap employed, if desired, before the mixture soproduced is introduced into the pulp, but in practice we refer to add tothe soap only so much alka i as will certainly be required, theremainder of the alkali being separately added to the mixture ifanalysis shows that such an addition is necessary.

The scrap leather employed in practicing our invention will contain inmost cases both bark-tanned and chrome-binned leather, so that it willusually be desirable to add a certain amount of soluble sulfidto thepulp mixture when a black leatherboard is wanted. The proportion ofsolid sulfid required will usually be about 5% by weight of thechrome-tanned leather scrap employed.

By the term chrome-tanned leather as herein used we intend to refer toall leather commercially known by that name, which is commonly used todenote any leather tanned by the use of inorganic chemical compounds ofvarious sorts.

Instead" of employing a soap compound as the source of the insolubleprecipitate which is deposited u on the fibers of the pulp we may usefor t e same purpose any one or more of a variety of other well-knownsubstances or compounds which will remain in solution when added to thepulp mixture and will ield an insoluble precipitate u on the additlon ofa suitable precipitant. "or example, a colloidal substance such asalbumen, casein, or gluten may be used for this purpose, as any of thesesubstances will be precipitated in insoluble form from the substantiallneutral pulp mixture by the addition 0 various precipitants well knownto chemists, including. the precipitants hereinbefore referred to.. Weprefer, however, to

kaline treatment, precipitating insoluble waterproofing compounds insand mixture, and subsequently forming the pulp into the desiredproduct.

2. The herein described rocess of producing a waterproof leatherl ioardwhich consisls in preparing a ulp mixture containing fibers of tannedleat er, renderingthe same receptive to waterproofing agents by analkaline treatment, mixing therewith a soluble compound of fatty acidsand alkaline bases, adding thereto a precipitant adapted to react withthe fatty acids to deposit an insoluble precipitate upon the fibers ofthe pulp, and subsequently forming the pulp into the desired product.

3. The herein described process of producing a waterproof leatherboardwhich consists in preparing a pulp mixture containing fibers of tannedleather, rendering the same receptive to waterproofing agents by meansof alkaline re-agents adapted to combine with the acids derived from theleather to form soluble compounds thereof, mixing therewith a solublecompound of fatty acids and alkaline bases, adding thereto aprecipit-ant adapted to re-act with said soluble comonj thefibers of thepulp, and su 3e pounds to deposit an insoluble precipitaite se uent yforming the pulp into the desired pro not.

4. The herein described process of producing a waterproof and coloredleatherboard which consists in preparin a pulp mixture containing fibersof tanne ing the same rece tive to waterproofing agents by an alka inetreatment, mixing pulp into the desired product.

5. A waterproof leatherboard made from pulp containing disintegratedfibers of tanned leather and having insoluble waterproofing compoundsdeposited by recipitation upon and thereby int-imatel; mixed with thefibers of which it is composed,.sub-

stantially as described.

In testimony whereof, we have hereunto subscribed our names this 27thday of January, 1909.

. EDGAR S. BUFFUM.

WILLIAM W. CARTER.

Witnesses:-

JOSEPH T. BRENNAN, E. D. Crnmwrox.

leather, render-

